Several bioadhesive drug delivery systems based on a variety of polymers have been described in patents and in literature. Majority of these patents concentrate on the adhesion of the drug to the gastric mucosa in order to retain the drug for a prolonged period of time in the target area. Such formulations tend to be solid products to be hydrated at the site of action for proper attachment to the tissue. Several polymers hydrate in presence of water and hydrophilic solvents and adhere to biological surfaces. These polymers alone or in combination with others polymers and active ingredients have been formulated for use in several commercial products. The first such commercial product based on a combination of gelatin, pectin and sodium carboxymethylcellulose in a hydrocarbon gel vehicle was marketed under the trademark Orabase.RTM. by Hoyt Laboratories, a division of Colgate-Palmolive Co. Similar product based on polyacrylic acid based polymer in water is marketed under the trademark Replens.RTM. by Warner-Lambert Co.
A composition containing 50 to 90 percent of cellulose ether and 5 to 50 percent homo or copolymer of acrylic acid is described in U.S. Pat. No. 4,226,848 as bioadhesive preparation for oral and nasal cavities. Acrylic polymer described in this patent is a lightly crosslinked acrylic acid allyl sucrose copolymer available under the trademark Carbopol.RTM.934 from B. F. Goodrich Chemical Co. Polyacrylic acids and their salts are also described in U.S. Pat. No. 4,226,484 at a concentration of 0.2 percent by weight as water-soluble polymers with desired viscosity.
Polyacrylic acid crosslinkced with divinylglycol commercially known as Polycarbophil is described in U.S. Pat. No. 5,225,196 as a bioadhesive polymer suitable for sustained release of medicaments. Bioadhesive water soluble copolymer of glycerol and methacrylic acid commonly known as polyglycerol methacrylate is described in U.S. Pat. No. 4,863,725.